JP-3138799-B describes a vehicle drive system that includes a left-wheel drive unit having a first motor for driving a left wheel of a vehicle and a first epicyclic transmission that is provided on a power transmission line between the first motor and the left wheel and a right-wheel drive unit having a second motor for driving a right wheel of the vehicle and a second epicyclic transmission that is provided on a power transmission line between the second motor and the right wheel. In the first and second epicyclic transmissions, the first and second motors are individually connected to sun gears, and the left and right wheels are individually connected to planetary carriers, ring gears being coupled to each other. Brake devices are provided for controlling the rotation of the ring gears by bringing the coupled ring gears into disengagement from or engagement with each other.
In the above-described vehicle drive system, a start assist control is executed when the vehicle is started by applying the brake devices. Further, after the vehicle is started, by executing a left and right opposite torque control so that the first and second motors produce torque in opposite directions with the brake devices released, even when a yawing moment is applied to the vehicle by disturbance, a moment that is opposite to the yawing moment is produced so as to increase the straight line and turning vehicle stabilities.
In recent years, there are strong demands for energy saving and improved fuel economy. In the vehicle drive system of JP-3138799-B, there is still room for improvement.